This invention relates to methods for producing construction material. More particularly, it relates to methods for producing construction material using enzyme producing bacteria.
The built environment is primarily constructed using a limited palette of traditional materials: clay, concrete, glass, steel, and wood. These traditional materials contain a high-embodied energy, with components of concrete and steel mined from non-renewable resources. Although wood can be grown and harvested in a renewable manner, harvesting, processing and transportation greatly contribute to carbon dioxide production and depend on large amounts of energy and fuel resources. Approximately, forty-percent of global carbon dioxide is linked to the construction industry, primarily due to material production and disposal. Biologically grown materials can be pollution free and contain a low embodied energy, if produced as part of a local ecosystem.
Commonly used throughout history, masonry construction continues to make up a large part of the built environment, utilized for both load bearing structures and veneer construction. According to Chaisson, globally, traditional clay brick manufacturing produces over 1.23 trillion units per annum with a heavy dependency on non-renewable natural resources. Clay brick manufactured in coal-powered kilns emits approximately 1.3 pounds of carbon dioxide per unit. According to Burke, in total, brick manufacturing emits over 800 million tons of man-made CO2 each year, and yet represents only one material currently used in building construction.
Fired clay bricks can be manufactured between 3-20 days, depending on the equipment and processes used. This range represents modern automated factories able to process bricks without manual labor, to the clamp method of bricks stacked around a burning fire used in many developing nations.
As an alternative to load bearing fired clay masonry, Concrete Masonry Units [CMU] are widely used as they are more economical, faster to manufacture and can serve as a structural typology for global construction. Comprised of concrete, these units are made with Portland cement, large aggregate and sand filler. According to Hanley of the United States Environmental Protection Agency, global carbon dioxide (CO2) emissions from cement production were approximately 829 million metric tons of CO2 in 2000.
According to DeJong, Natural cement is created through chemical deposition and chemical processes associated with weathering, and can be found in various locations on the earth's crust. The formation of natural sandstones is primarily attributed to the precipitation of calcite cement.
Urease producing Sporosarcina Pasteurii a nonpathogenic, common-soil bacterium has the ability to induce the production of calcite through a chemical reaction, fusing loose aggregate. A hardened material is formed in a process referred to by Stocks-Fischer as microbial induced calcite precipitation [MICP]. Applications include environmental stabilization of contaminated soils, and encapsulation of hazardous and other contaminants in natural soils and acid mine tailings. Ramachandran and Jonkers have proposed the use of microbes to remediate cracks in concrete structures and the repair of cracks in monuments. According to DeJong and Whiffin, civil engineering researchers in the United States, Australia and the Netherlands have proposed the use of MICP for soil stabilization and erosion control.